(1) Technical Field
This invention generally relates to electronic circuitry, and more specifically to frequency based integrated circuits having at least one integrated tunable filter.
(2) Background
A large number of modern electronic systems, such as personal computers, tablet computers, wireless network components, televisions, cable system “set top” boxes, and cellular telephones, include frequency based subsystems such as radio frequency (RF) transceivers. Many of such RF transceivers are actually quite complex two-way radios that transmit and receive RF signals across multiple frequencies in multiple bands; for instance, the 2.4 GHz band is divided into 14 channels spaced 5 MHz apart, beginning with channel 1 which is centered on 2.412 GHz. As another example, a modern “smart telephone” may include RF transceiver circuitry capable of concurrently operating on different cellular communications systems (e.g., GSM and CDMA), on different wireless network frequencies and protocols (e.g., IEEE 802.1bg at 2.4 GHz, and IEEE 802.1n at 2.4 GHz and 5 GHz), and on “personal” area networks (e.g., Bluetooth based systems).
In addition, such RF transceivers often operate in “noisy” RF environments, which includes other devices with RF transceivers (e.g., wireless networks, cellular telephones and cell towers, and personal area networks), as well as devices that emit electromagnetic interference on frequencies of interest (e.g., microwave ovens). For example, in the United States, devices that use the 2.4 GHz band includes wireless “WiFi” networks, microwave ovens, ISM band devices, security cameras, ZigBee devices, Bluetooth devices, video senders, cordless telephones, and baby monitors.
Designing frequency based electronic systems or subsystems capable of operating across multiple frequencies and multiple bands in noisy environments is a significant challenge, particularly in integrated circuit solutions, which are desirable from a cost, reliability, size, and low power perspective. The apparatus and method described below provide a frequency based integrated circuit solution that selectively filters out unwanted bands or regions of interfering frequencies utilizing one or more integrated tunable notch or bandpass filters or tunable low or high pass filters. Various aspects of the apparatus and method described below will be seen to provide additional advantages.